Abstract Microfluidics has revolutionized the world of medicine by creating new ways of investigating single cells and is steadily becoming the transformative field dreamed of for many years. Clinical tests relying on large volumes (i.e. 1 liter) of biological fluid is one challenge yet to be confronted in microfluidics. There are a number of important samples such as peritoneal lavages or urine where large fluid volumes must be processed in order to collect enough cells for proper diagnoses. Current batch processes are lossy, cum- bersome and vary by user. This work will develop a novel microfluidic technology to significantly con- centrate and isolate cells from large fluid volumes. The goal is to develop an automated, highly sensitive and extremely high throughput technology for reducing the volume of these samples to allow scientists easy access the clinically relevant material, improving the current detection techniques and providing for future advancements in diagnostics and treatments. The ability to process large volumes of bodily fluids and extract rare and dilute cells, will enable multiple diagnostics and prognostic tests to monitor and early diagnose cancer with important benefits to patients. The technology will rely upon a fundamental fluid dynamics phenomena known as inertial focusing. The passive phenomena can be exploited to locate and concentrate cells in particular locations within a fluid channel, which allow for easy removal of cell free fluid. While inertial focusing has been known since the 1960s it is not completely well understood, especially with biological samples in complex device geometry. The work will use engineering principles and detailed simulations, validated by experiments with model cells, in order to optimize device performance. The final device will consist of multiple mi- crofluidic stages which makes the final design space complex. The number of parameters is too large to explore by experiment alone. The specific aim is to design and experimentally validate a microfluidic inertial focusing device capa- ble of reducing 1 liter of fluid to 1 milliliter while retaining all cells of interest.